1. Field of the Invention
The present invention generally relates to a scanning mechanism, and more particularly, to a scanning mechanism of an optical scanning module
2. Description of Related Art
Along with the progress of hardware and software, a scanner has become one of the basic equipments for a computer user, by which test data or image data such as file, magazine, book and picture can be scanned for further processing.
Among various scanners, a flatbed scanner is the most often one. To scan a file, a transmission mechanism including a motor, a set of gears disposed on a scanning unit and a transmission belt is required to drive the above-mentioned scanning unit, so that the scanning unit slips along a guiding shaft to accomplish scanning job on an object horizontally placed over the scanning unit.
In the mechanism however, since the above-mentioned motor, transmission belt and the set of gears are usually disposed at a side of the guiding shaft with a distance from the guiding shaft so that when the motor drives the scanning unit through the transmission belt, a torsion moment on the scanning unit is caused by the transmission belt. The torsion moment makes the scanning unit unable to move in parallel along the guiding shaft. As a result, the moving distances of both sides opposite to each other of the scanning unit are not the same so as to make the quality of the scanned image unstable.